Mystery noise in uv

[chrisjj]

Is there a Milkdrop 2 preset author who could try the attached test preset for me and post a screenshot of the result?

It's a blank preset with this one-line warp shader:

ret = (uv.y*5000)%2 < 1;

in a window 416 pixels high (as shown by the monitor at top right).

Here, the output id this:



(or a variant, depending on window height) continually changing, not a static pattern of unbroken horizontal lines as expected.